Radio controlled aircraft system



Sept 26, 3939 F. J. 'HOQVEN RADIO CONTROLLED AIRCRAFT SYSTEM Filed July 17,1936 2 Sheets-Sheet 1 INVENTOR.

kph 26, 193%. F. .2. HQCVEN 293735341 RADIO CONTROLLED AIRCRAFT SYSTEH Filed July 17, 1936 2 Sheets-Sheet 2 INVENTOR. fiedey'z cfi Jifio we 22, B Y 3 v I ?atented Sept 2c, 1939 2,173,841

PATENT OFFICE 1: am srs'rniu Frederick .1. Hoover, Dayton, ohio Application July 17, race, Serial No. 91,191 7 Claims. (01. 172-282) My invention relates broadly to radio conceived from a directively propagated radio fretrolled systems for aircraft and more particularly quency beam.

to a circuit arrangement or mechanical structure Other and further objects of my invention refor automatically maintaining an aircraft on a side in the multiple speed control system for predetermined course of flight. operating the rudder of an aircraft as set forth One of the objects of my invention is to provide more fully in the specification hereinafter followa circuit arrangement for automatically controling by reference to the accompanying drawings, ling the course of aircraft in flight between two in which: or more prearranged positions with means for Figure 1 diagrammatically and schematically automatically restoring the aircraft to the proper shows the circuit arrangement of my invention 10 course in the event of any tendency of departure and the means employed for operating the airfrom such prearranged course. craft rudder from the same motor which orients Another object of my invention is to provide a the radio compass loop; and Fig. 2 illustrates the radio controlled system for aircraft having means manner in which the system of my invention confor operating the rudder of an aircraft for maintrols a servo-motor which, in turn, controls the taining the aircraft on a predetermined course rudder of the aircraft for maintaining the airwith means for eliminating the effects of huntcraft on a prearranged course determined by the ing and lost motion which may tend to arise durdirectively propagated radio f q y heaming the functioning of the control mechanism. y invention is directed to a System for aute- 0 Still another object of my invention is to promatically guiding an aircraft for maintaining the vide an arrangement of control mechanism for aircraft along a prearranged course of flight deguiding aircraft according to a directively propat m by a e t v ly p pa at d o egated beam having means for correspondingly quency beam. Accidents due to the failure of controlling the position of the aircraft rudder p s to P pe y e ow e directively P whereby the rudder may be maintained in a gated beam may be avoided in the system of my position which will set the course for the aircraft ent o by el m a e hu e eme t according to the directively propagated beam which may introduce sources of error in the readand will be automatically adjusted to maintain ing o in i a Observing received beam the aircraft on the predetermined course irres gnals. In addition to visual and aural si spective of conditions tending to deviate the airobserving mea s, I Provide an automatic control so craft from the course. for directly maintaining the rudder of the air- A further object of my invention is to provide craft on the course defined by the directively a circuit arrangement for a precision control propagated beam- U de ha es in w nd eonmechanism for guiding aircraft according t ditions, the tendencies which exist for deviating directively propagated beam of radio frequency an aircraft from the predetermined u s pr 35 energy having means for controlling the angular @1109 110 detrimental efieet in e System Of my position of the rudder of the aircraft in difierinvention. The a at ie tin means tendential relation to the deviation of the aircraft ing to maintain the radio compass oop n a prefrom the prearranged course. determined plane with reference to the line of A still furthe object, of my invention is t bearing of the beam or transmitting station to- 4 vide a precision control mechanism for aircraft ward which the aircraft is directed controls the having means for angularly shifting the rudder angular position of the rudder on the F I of the aircraft with substantially greater angular may employ the same motor which onents the velocity when the aircraft deviates or tends to deradio compass 100p for controlling the movement vie-e a relatively great distance from Prer- 2232iit???ti;icttififiitftftfifitiifini 0i igg ff jz g i 22 52 3 2 g g s a radio compass loop which, in turn, controls the r er s y W e e a movement of the rudder. when the loop is oilcraft departs a relatively short distance from the course with respect to a line of direction from prearranged the loop to the distant radio transmitter, the 5 st1n another oblect of my invention is to P orientation means operates relatively quickly. Vlde an arrangement of radio control precision w t plane f t loop is moved into p051. pp s for Operating a Serve-motel which, tion on-course with respect to the transmitter, in turn, controls the angular movement of the the driving means operates more slowly. This 5 rudder of an aircraft under control of energy revariable speed arrangement insures a quick and 55 m. n t

accurate response of the receiving apparatus to the signals of the transmitter. That is, the orien tation is effected at greater speed when the loop is off-course with respect to the line of bearing to the distant transmitter than when the loop is closer to the on-course relation to the line of bearing between the loop and the transmitter.

The radio compass loop on the aircraft drives a drift indicator which informs the pilot with respect to the functioning of the automatic control system. A brake is employed for insuring the setting and maintaining of the rudder in the angular plane determined by the position of the radio compass loop which brake is functioned simultaneously with the deenergization of the driving motor circuit. In certain installations, I provide a servo-motor which directly controls the rudder of the motor is controlled in accordance with the orientation of the loop which is maintained in predetermined position according to the position of the aircraft with respect to the directively propagated beam.

Referring to the drawings in detail, Figure 1 shows the apparatus carried by the aircraft for maintaining the aircraft on the course defined by the directively propagated beam. Reference character I designates the non-directional antenna connected to input system 2 of the radio compass receiver 3.on the aircraft. The receiver is connected to ground as indicated. The output of the receiver has been indicated connected to terminals 4 and as connected to both the aural receiving device, such as telephones 5, and also relay device 6. The relay device 6 comprises armature winding 1 angularly movable within the electromagnetic structure 8 having control windings 9 and Ill. The angularly shiftable arm II is moved under control of the armature winding 1 and carries opposite contact members I2 and I4 adapted to make contact respectively with fixed contacts I5 and I6. The fixed contacts I5 and I6 may' comprise magnetic elements coacting with contacts I2 and I4 formed from magnetic material so that the arm II when shifted to either of the limiting positions thereof remains in the shifted position. By reason of the stick magnetic characteristic of the device, I provide special means for restoring the arm II to central position. Restoring means comprises a yokeshaped member I1 carried by pivoted arm I8 pivoted at I9. The pivoted arm I8 has an armature 20 thereon which may be operatively controlled by means of electromagnet 2| against the action of spring means '22.

The operation of the restoring mechanism will be clearer after a consideration of the loop actuating mechanism. The coil antenna or loop or directional antenna 23 is mounted on an angularly shiftable or rotatable shaft 24 which is suitably geared to a driving motor system. For purposes of explaining my invention, I have shown the loop orienting mechanism schematically as comprising a worm gear 25 for driving gear 26 connected with rotary shaft 24, but it will be understood that various forms nism may be provided. The comprises field magnet system 28, field winding 29 and the rotary armature 30. ing 29 is tapped at 3I as indicated. In order to control the direction of rotation of the driving motor 21, I provide automatic reversing switches 32 and 33, which are individually controlled by electromagnetic systems 34 and 35 dependent upon the movement of arm II to the left or right,

aircraft and in which the servo-- respectively. That is to say, the arm I I in movin to the left establishes a connection between mov able contact I2 and fixed contact I5, thereb;

completing a circuit through conductor 1 through electromagnetic actuating device 34 thu energizing electromagnetic actuating device 3 from potential source 36 through the circuit com pleted through conductor 14 returning to arm I as shown. In the event that arm II shifts to th( right, a connection is established between movable contact I4 and fixed contact I6 through conductor 15 which leads to electromagnetic actuating device 35 and through conductor 16 to poten tial source 36 returning to arm I I through conductor 14. The source of potential 31 for driving motor 21 is reversed with respect to the armature winding 30 under control of the reversing switches 32 and 33 for determining the direction of rotation of the driving gear 25.

The arm members H are pivoted at a common point which is the intersection of the V structure shown within the arms of the yoke shaped member I1. When yoke shaped member I1 moves upward under the influence of electromagnet 2I,

together thus restoring the contact arm II to its central position. The means for causing the arms to become operativeonly when the radio compass loop approaches the on course position through electromagnetic relay 39 which at the same time controls the speed of motor 21, constitutes a useful improvement in the art.

In order to control the rate of movement of the driving gear 25 depending upon the angular relation of coil antenna 23 to the direction of the radiant energy source, I provide .a relay 38 comprising a magnet 39, an armature 40, and a spring 4I. Relay 38 is marginal; i. e., spring H is so adjusted that when the current through be pulled away magnet, thereby establishing electrical contact between armature and contact 42. When the current in magnet 39 exceeds a certain fixed value, the armature is pulled toward magnet 39, establishing contact between armature 40 and contact 43. The restoring means applied to relay 8 which consists of yoke I1, arm I8, pivot I9, armature 2U, magnet 2I, previously referred to, is operated from potential source 44 through rotating contactor 45 driven by motor 46 in such a fashion that the arm II of indicator 8 is periodically restored to the central position. The circuit through magnet 2 I extends through conductor 16 to interrupter 45 to one side of potential source 44. The opposite side of source 44 connects through conductor 11 to armature 40, the circuit from which is completed through either contact 42 or 43, depending upon the position of the armature. When the armature 40 is attracted by magnet 39 to establish contact with contact 43, the restoring process takes place, that is, during such time as the current in coil 39 exceeds the aforementioned predetermined value. When armature 40 is in contact with contact 43, a circuit to magnet 2| is completed through conductor 18. I i i I provide means for modulating the radio frequency current in loop 23 by means of a balanced modulator consisting of electron tubes 41 and 48. The cathodes 49 and 50 of these tubes are connected to opposite ends of the secondary of a transformer whose primary is connected to oscillator 5| and the electrical center of whose secgreat, I have ndary is connected to ground at 52. The anodes 3 and 56 of tubes 31' and 48 are connected to oupling coil 55 so that the signal from loop 23,

'hich is impressed on grids 56 and 51 of tubes 41 nd 48 through coupling condensers 58 and 59, is iodulated by the frequency of the oscillator 5| .nd impressed through coupling coil 55 on the nput circuit of receiver 3 simultaneously with he signal from the non-directional antenna I. [he combined signals are amplified and demodllated by radio receiver 3 and the resulting alteriating current of the frequency of oscillator 5| s impressed on the moving coil 1 of the indicator 3 in the manner set forth in detail in my copendng application Serial Number 90,996, filed July l6, 1936, for Radio compass system,

The actuating coils 9 and N1 of the relay 8 are :onne'cted to the secondary of the transformer 5la so that magnetic flux is impressed upon the magnetic circuit of relay device 6. It will be seen that there will be present in the output circuit 9 of radio receiver 3 a current whose frequency is that of oscillator 5|, the amplitude of which is proportional to the signal picked up by loop 23 and, therefore. proportional to the angle of deviation of loop 23 from the line to the source of radiant energy, and the phase angle of which, with respect to the current in coils 9 and i6, is dependent on the phase angle of the radio frequency current picked up by loop 23 with respect to the radio frequency current picked up by nondirectional antenna l, and whose phase anglewith respect to coils 9 and I is, therefore, a function of the direction of deviation of loop 23 from the line to the source of radiant energy. It will then be seen that the movable arm connected to coil 1 will move to the left or to the right in accord with movement of loop 23 to the left or to the right of the line to the source of radiant energy.

The magnetic switches 32 and 33 are so connected to motor 21 and source 31 that when the loop 23 rotates to the left and the relay 8 moves also to the left, the motor 21 will be caused to turn the loop to the right. Conversely, if the source of radiant energy in eifect moves to the left by deviation of the aircraft from the course, the loop will then turn to the left of the line between the loop and said source. Arm i will then move to the left, switch 32 will then close, and the loop will be caused to turn to the right. Because of the magnetic attraction existing between fixed magnetic contacts l and I6 and magnetic contacts l2 and M flxed to arm ll, it is necessary that the restoring means ll be actuated intermittently when the magnetic control winding 29 is energized by virtue of the current flow incident upon the impression of signal energy on the balanced amplifier circuit from loop 23.

I have pointed out that the intensity of the signal which actuates relay 6 is proportional to the degree of deviation of the plane of the loop 23 from a line extending in the direction of the source of radiant energy. In order that this signal may not become any greater than that required for the actuation of relay 6, when the deviation of the plane of the loop 23 from the line extending in the direction of the source is provided means whereby the sensitivity of tubes 41 and 68 may be decreased by the signal in the output circuit 6 if the signal amplitude delivered by the radio receiver 3 exceeds this desired value. Connected to the output circuit 6 of the radio receiver 3 is the anode of rectifier 69. Cathode 6| of the rectifier 60 is maintained by means of potentiometer 62 connected between source 63 of high potential and ground at 86 at a constant positive potential with respect to current which is equal to the peak value of that signal necessary to give the desired deflection of relay 6, so long as the value of that signal which is also impressed on plate 10 of rectifler 60 does not exceed the amount necessary to deflect relay 6. Anode 19 will then be negative at all times with respect to cathode SI, and no current will flow through rectifier 6']. Whenever the signal energy impressed on coil 1 exceeds the said predetermined value, the anodelll will become positive with respect to cathode 6| and current will flow through rectifier 6|! from anode 10. Current flowing from ground through resistance 65 to anode 1U thence to cathode 6| through potentiometer 62 back to ground, causes anode 10 to assume a mean potential with respect to ground, thereby charging condenser 66 through resistance 61 negatively with respect to ground. This negative potential is communicated through resistances 68 and 69 to grids 56 and 51 of tubes 61 and 91, thereby decreasing the transconductance directly in proportion to the amount by which the signal impressed on coil 1 exceeds the predetermined positive potential of cathode '61. In this manner, the modulated energy transmitted to radio receiver 3 from loop 23 through coil 55 is limited when its value exceeds that necessary to actuate the relay 6.

It will be understood by those skilled in the art of electron tubes that when the negative charge is impressed on grids 56 and 51 that the anode current of tubes 61 and 48 will be decreased in proportion to the magnitude of the negative charge. It then follows that when loop 23 is at an angle to the line between the loop andthe source of radiant energy greater than that necessary to provide adequate actuating means for relay 6, the plate current in tubes 31 and 48 will be decreased proportionately. The anode currents of tubes 61 and 98 flow through magnet 39 and the predetermined value referred to above in connection relay 38 is that value of the combined plate current of tubes 91 and 68 which is obtained when the loop 23 is on or adjacent to the line of the source of radiant energy. Thus, when the angle of the loop with respect to said line exceeds that value where the signal in coil 1 is adequate to control relay 6, relay 39 will open due to the reduced plate currents in plates 41 and 68 as explained hereinbefore, thereby closing the contact 82 when armature 10 is short-circuiting a part of the field coil 29 of motor 21, causing m0- tor 21 to run at high speed. When the loop 23 is turned by means of 'gears 25 and 26 as has been explained above, and as the loop approaches the line to the source of radiant energy, the plate current in tubes 41 and 48 will cause the magnet 39 to pull armature 40 with suflicient force to overcome the force of spring 4|, thereby establishing a connection between armature 40 and contact 43 which removes the short-circuit from the portion of the field coil 29 and thus causes the motor 21 to run slowly, at the same time completing the circuit through the magnet 2I, source 49, interrupter 45. Thus, there is initiated into operation, the mechanical restoring means or yoke H which will periodically restore the indicator arm II to the center point between fixed contacts l5 and I6 by means of relatively movable arm members 1| until such time as loop 23 shall be in a plane normal to a line drawn to the source of radiant energy, and

with the description of the signal will disappear in output circuit 4 and the system will come to rest at equilibrium. Thus, I have established that when the loop is near the desired orientation, the speed of its motor will be slow and the interrupting mechanism will function, but when the loop is far from the desired course, the operating motor will operate at high speed and the relay will notbe interrupted by the restoring mechanism.

The shaft 24 of the loop 23 carries gear 26 which is driven by.the worm 25 on the shaft which is driven by motor 21. The shaft 80 carries a drum 8i against which a brake mechanism 82 is adapted to function. The brake mechanism 82 includes a member 83 which carries a brake shoe 84 which engages drum 8! and which is normally urged in engagement with drum BI by means of spring "I9. The member 03 carries an armature 85 which is magnetically acted upon by electromagnet 86. Electromagnet 86 is connected in series with the armature winding 30 so that when armature winding 30 is energized for revolving shaft 80, electromagnetic winding 86 is similarly energized for moving brake shoe 84 out of engagement with the surface of drum BI allowing shaft 24 to be revolved by insuring that shaft 24 is brought to an immediate stop as soon as armature winding 30 is deenergized. The shaft 24 extends downwardly beyond gear 26 to the differential gear system 81. The differential gear system 81 includes bevel gear 88 connected with shaft 24, bevel gear 89 connected with shaft 90, and intermediate beveled gears 9I and 92. Intermediate bevel gears 9i and 92 are connected with an indicating pointer 93 operative over a calibrated scale 4. The movement of pointer 93 with respect to scale 94 serves to provide a drift indicator. THe drift indicator is provided with a calibrator in accordance with the performance of the aircraft under control of the mechanism which I have provided for controlling the aircraft.

Shaft carries crossarm 95 to the ends of which the control cables 96 connect extending to the steering member 91 of rudder 98. The angular position of rudder 98 is controlled by motor 27 simultaneously with a control of the angular position of loop 23. Loop 23 is maintained in a plane normal to the line of flight so that it is apparent that the direction of flight of the aircraft will be corrected in the event that the aircraft should tend to drift from the predetermined course because of the corrective movement imparted to the rudder 98 through the movement of shaft 90.

Under circumstances where It is necessary to control the rudder from a separate servo-motor, I employ the arrangement illustrated in Fig. 2. The shaft 24 which extends from the radio compass loop 23 carries in insulated relation thereon the contact arm I00. Contact arm I00 is operated through a relatively short angular distance to establish connection with either of two contacts IM or I02 which are supported in insulated relation by arms I03 and I04 supported on shaft I05. Shaft I05 carries gear I06 which is driven by worm I07 on shaft I08. Shaft I08 is connected with rotary armature I09 of the rudder motor II 0. Rudder motor H0 is reversible under control of motor field winding III having a center tap connection H2. The source of potential for driving the motor is indicated generally at H3. The direction of current flow through field winding II I depends upon the contacting of contacts II4 carried by arm I00 either with contacts IM or I02 dependin upon the angular movement of radio compa: loop 23. It will be understood that the separa tion I have shown of contacts IN and I02 merely for the purpose of simplifying illustratio and that the actual separation employed is ad justed to meet practical conditions. The arma ture winding on armature I09 is connected i1 series through electromagnetic winding 99 wit] the angularly shiftable arm I00 which is adapter to move contact II 4 either into connection witl contact IM or I 02 for determining the directlor of current flow through the field and armatun winding for correspondingly determining the direction of movement imparted to shaft I05. Ii will be seen that arms I03 and I04 so rotate contacts IOI' and I02 that these contacts are always in the orbit in which contact II 4 revolves. During the periods of time when the reversing operation is being effected or when the rudder must remain stationary, shaft I 05 is locked against rotation by the engagement of brake shoe I I5 with brake drum IIS on shaft I08. Brake shoe H5 is carried by pivoted member I I! which is normally urged by spring II8 into engagement with the circular periphery of brake drum I I6. Member I I7 carries armature II9 which is attracted by electromagnetic Winding 99 when the motor circuit is energized for withdrawing the brake shoe II5 from the drum H6 and allowing motor H0 to impart movement to shaft I05. Shaft I05 drives shaft I20 through the differential gear system I2I. Differential gear system I2I includes bevel gear I22 carried by shaft I05 and bevel gear I23 carried by shaft I20. ate bevel gears I 24 and I25 are carried on pointer I26 which operates over calibrated scale I21 to indicate drift of the aircraft from the predetermined course. The shaft of pointer I26 is terminated in a handle member I32 as shown in Figure 1, which. handle member can be manipulated for the purposes already set forth. Shaft I20 carries cross-arm I28 which connects through cables I29 with opposite ends of steering arm I30 connected to rudder I3I. Rudder I3I is, therefore, controlled from motor ance with the angular position of the loop 23 which is maintained through the operation of motor 21 in a plane normal to the course of flight. Accordingly, my invention provides means for maintaining an aircraft in a predetermined course either through control of the radio compass driving motor or through a servo-motor in accordance with my invention as herein described.

I realize'that modifications may be made in the construction of the control mechanism and the circuit arrangements employed therewith and, while I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is as follows:

1. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver including a coil antenna, means controlled by said radio compass receiver for orienting said coil antenna according to the directive characteristics of the received signaling energy, means H0 in accord-' Intermedicontrolled by the movement of said coil antenna 7 for controlling the operation of said mechanism, means for operating said mechanism at different speeds depending upon the bearing of the coil antenna with respect to the direction of prop-.- agaticn of the signaling energy and a differential gear system interposed between the means controlled by the movement of the coil antenna and said mechanism.

2. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver including a coil antenna, means controlled by said radio compass receiver for orienting said coil antenna according to the directive characteristics of the received signaling energy, means controlled by the movement of said coil antenna for controlling the operation of said mechanism, means for operating said mechanism at two different speeds depending upon the bearing of said coil antenna with respect to the direction of propagation of the signaling energy and a drift indicator interposed between said means controlled by the movement of said coil antenna and said mechanism.

3. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver connected therewith, a coil antenna, a local oscillator whose output is controlled according to the bearing of said coil antenna with respect to the transmitter, means for orienting said coil antenna, means for controlling the aforementioned means by the output of said local oscillator according to the directive characteristics of the received signaling energy, means controlled by the movement of said coil antenna for controlling the operation of said mechanism, means for operating said mechanism at a greater velocity when the aircraft is substantially off-course with respect to the direction of propagation of the signaling energy than when the aircraft is more nearly on-course with respect to the direction of propagation of the signaling energy, and a drift indicator interposed between said first mentioned means and said mechanism.

4. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver including a coil antenna, drive means controlled by said receiver for orienting said coil antenna according to the directive characteristics of the received signaling energy, means for imparting movement from said drive means to said mechanism, means for modifying the rate of operation of said drive means according to the bearing of said coil antenna with respect to the direction of the directively propagated signaling energy, and a differential drift indicator interposed between said mechanism means.

and said drive gation of the signaling energy,

in output of said 5. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver including a coil antenna, drive means controlled by said receiver for orienting said coil antenna according to the directive characteristics of the received signaling energy, means for imparting movement from said drive means to said mechanism, means for angulariy moving said drive means at different speeds depending upon the bearing of the coil antenna with respect to the direction of propagation of the signaling energy, and a drift indicator disposed between said mechanism and said drive means.

6. A system for controlling aircraft comprising in combination with the rudder of an aircraft, mechanism for controlling the angular movement of said rudder, a radio compass receiver connected with a coil antenna, an oscillator, means for controlling the amplitude output of said oscillator according to the amplitude of the signal energy incident upon said coil antenna, means controlled by the combined output of said local oscillator and the output of said radio compass receiver for orienting said coil antenna according to the directive characteristics of the received signaling energy, a current limiting circuit connected with said local oscillator for limiting the effect of said oscillator upon said aforementioned means, means controlled by the movement of said coil antenna for controlling the operation of said mechanism, means for regulating the rate at which said mechanism is controlled depending upon the bearing of the coil antenna with respect to the direction of propaand means for restraining the displacement of said rudder so long as said coil antenna maintains a predetermined relation to the direction of the directively propagated signaling energy.

'7. A system for the automatic steering of aircraft comprising a radio receiver, a directional antenna associated therewith, a non-directional antenna in circuit with said receiver, means for modulating the signals of said directional antenna, a course indicating means connected to the output of said receiver, rudder control means, including an electric motor in circuit with said indicating device, means responsive to off-course indications for causing said motor to operate, means for rotating said directional antenna, said rudder control means being operative upon movement of said directional antenna from a predetermined relation with respect to a transmitting station and means responsive to a change modulating means for changing the speed of rotation of said directional antenna.

FREDERICK J. HOOVEN. 

